The present invention relates to a surface mounted light emitting diode.
Light emitting diodes of this type are known such as the device shown in FIG. 11. In the light emitting diode 1 shown in the figure, a pair of external connection electrodes (a cathode electrode 3 and an anode electrode 4) are formed by patterning on the upper surface of a glass epoxy substrate 2, and a light emitting diode element 6 is then fixed on top of the cathode electrode 3 with an electrically conductive adhesive 5. The upper surface electrode of the light emitting diode element 6 and the anode electrode 4 are connected with a bonding wire 7, and the bonding wire 7 and the light emitting diode element 6 are sealed with a resin sealing body 8. To enable subsequent use, the light emitting diode 1 is then mounted on a motherboard 11, and lower surface electrodes 9, 10, which are merely a portion of the external connection electrodes, are then fixed with solder 14 to printed wiring 12, 13 on the motherboard 11 to complete the surface mounting process.
However, in the conventional light emitting diode 1 described above, the overall height dimension h1 following mounting on the motherboard 11 includes the board thickness of the motherboard 11 plus the thickness of the glass epoxy substrate 2 and the resin sealing body 8 of the light emitting diode 1, and as such is unable to sufficiently meet the demands for thinner devices.
Furthermore, in the conventional light emitting diode 1 described above, the light emitting diode 1 is mounted on the motherboard 11 in an upward facing direction, and because light emission occurs through the resin sealing body 8, prolonged use of the light emitting diode 1 leads to a reduction in light emission intensity due to factors such as a deterioration in the resin sealing body 8 due to the ultraviolet light.
An object of the present invention is to provide a surface mounted light emitting diode which when mounted on a motherboard suppresses the overall height dimension including the motherboard to a minimum, enabling a shift to thinner devices.
Furthermore, another object of the present invention is to provide a highly reliable light emitting diode which does not suffer from a reduction in light emission intensity, even with continued use over prolonged periods.
A light emitting diode according to the present invention is a light emitting diode prepared by mounting a light emitting diode element on an upper surface of a base material, and then protecting the light emitting diode element with a resin sealing body, wherein a transparent body is provided in the aforementioned base material which extends from the upper surface through to the lower surface thereof, the light emitting diode element made of a gallium nitride based compound semiconductor with a transparent element substrate is fixed on top of the transparent body using a transparent adhesive, and a non-transparent section is provided above the light emitting diode element, and light emitted from the light emitting diode element passes through the transparent body and is guided out through the lower surface of the base material.
According to this invention, because light emitted from the light emitting diode element passes through the transparent body and is guided out through the bottom surface of the base material, by mounting the light emitting diode upside down on the motherboard, light can be irradiated in an upward direction from the motherboard. Moreover, by dropping the light emitting diode down into a hole formed in the motherboard, the overall height dimension of the light emitting diode, including the thickness of the motherboard, can be reduced to a value smaller than conventional surface mounted devices.
Furthermore, in a light emitting diode according to another aspect of the present invention, a through hole is provided in the aforementioned base material which extends from the upper surface through to the lower surface thereof, and the aforementioned transparent body is formed by filling this through hole with a transparent resin.
According to this invention, because light emitted from the light emitting diode element passes through the transparent resin filling the through hole in the base material and is guided out through the bottom surface of the base material, the emitted light does not diffuse and displays good directivity.
Furthermore, in a light emitting diode according to yet another aspect of the present invention, a fluorescent material comprising an yttrium compound is dispersed and mixed into at least one of the aforementioned transparent body and the transparent adhesive.
According to this invention, because a fluorescent compound comprising an yttrium compound is incorporated in either the transparent body which makes up all, or a part of the base material, or in the transparent adhesive used for fixing the light emitting diode element, and enables the generation of white colored light, surface mounted white colored light emitting diodes can be produced which are thinner than conventional devices.
Furthermore, in a light emitting diode according to yet another aspect of the present invention, a condenser lens section is provided on the lower surface of the aforementioned base material, below the transparent body.
According to this invention, by providing the condenser lens section, light passing through the bottom surface of the base material is condensed, improving the light emission intensity another level.
Furthermore, in a light emitting diode according to yet another aspect of the present invention, the aforementioned base material is any one of a glass epoxy substrate, a transparent resin substrate and a transparent glass substrate.
According to this invention, by making the light emitted from the light emitting diode element passes through the transparent glass substrate side which is less likely to deteriorate on exposure to ultraviolet light, light emission of a good intensity level can be maintained even after prolonged use.
Furthermore, in a light emitting diode according to yet another aspect of the present invention, the aforementioned non-transparent section provided above the light emitting diode element is either one of a pair of light blocking electrodes provided on the upper surface of the light emitting diode element, and a reflective film covering the outer surface of the transparent resin sealing body.
According to this invention, light emitted from the light emitting diode element is guided efficiently through the lower surface of the base material.
Furthermore, in a light emitting diode according to yet another aspect of the present invention, when the light emitting diode is mounted on a motherboard, the light emitting diode is mounted upside down with the resin sealing body dropping into a hole provided in the motherboard, and the periphery sections of this hole connect the external connection electrodes of the light emitting diode with the wiring pattern of the motherboard.
According to this invention, when the light emitting diode is mounted upside down on the motherboard, by soldering the aforementioned external connection electrodes to the wiring pattern on the motherboard, current can be carried to the light emitting diode element, and so the mounting operation is extremely simple. Furthermore, the height dimension by which the light emitting diode protrudes from the motherboard can be reduced dramatically.